1. Field of the Invention
The invention is related to pneumatic valves and in particular to a microminiature valve compatible in size and materials with current integrated circuit technology.
2. Prior Art
The need for small pneumatic valves for use in conjunction with integrated circuits is exemplified by Terry et al in their publication "A Chromatographic Air Analyzer Fabricated on a Silicon Wafer" IEEE Transactions on Electronic Devices, Vol. ED 26, No. 12, December 1979. In this publication Terry et al discloses a miniature valve made on a silicon wafer having a nickel diaphragm actuatd by a solenoid plunger. In contrast to the metal diaphragm taught by Terry et al, Greenwood, U.S. Pat. No. 4,293,373, and Guckel et al, U.S. Pat. No. 4,203,128, disclose techniques for forming flexible diaphragms from silicon wafers by diffusing boron into the surface of the silicon wafer in the region where the flexible diaphragm is to be formed. The undoped silicon is then preferentially etched away leaving a flexible diaphragm in the boron diffused region. Guckel et al additionally discloses a two part valve using a boron doped flexible diaphragm. Alternatively, K. E. Peterson in his article "Dynamic Micromechanics on Silicon: Techniques and Devices" IEEE Transactions on Electron Devices, Vol. ED-25, No. 10, October 1978, discloses a method for making miniature cantilever beam devices using silicon dioxide layers on a silicon substrate. In these devices, the silicon underlying the silicon dioxide layer is etched away to form a well under the unetched silicon dioxide beam. Petersen also teaches electrostatic deflection of the cantilever beams using a metal electrode deposited over the top surface of the silicon dioxide beam. In contrast to the solenoid plunger deflection of the membrane as taught by Terry et al, Brandt in U.S. Pat. No. 3,936,029, teaches a pneumatic amplifier in which the diaphragm is disposed between an operating chamber and a signal chamber. The pressure in the signal chamber displaces the membrane which varies the fluid conduction through the operating chamber.
The invention is a multi-layered integral microminiature valve which is compatible with current silicon wafer processing technology and eliminates the nickel diaphragm and solenoid actuator in the microminiature valve taught by Terry et al.